So we just moved into a new home 3 months ago, just getting into the heating season now and running into issues. I worked previously (15 years ago) as a service tech/install monkey for an oil company, so not flying completely blind here. First time poster here though!
System 2000 oil fired
3 heat zones (2 on first floor, 1 on 2nd floor)
Indirect hot water 40g storage tank (plate exchanger off boiler)
Horizontal mounted pressure tank, (hot on top, cool on bottom, assuming bladder is still intact) air relief valves on both supply and return side of boiler
No good means of manual air elimination/purging the zones via drains on the individual zones (my preference)
So the pressure relief on the boiler had been incessantly leaking, and I had kept the auto water feeder manually shut off, and topped it off every few days. Crud gets in the valve, and it drips, nothing new. Replaced the valve, no help, kept dripping. Dialed back the set pressure on the auto water feeder to 10psi. If I leave the feeder valve off, cold, the system sits at 0psi, and then begins to develop water hammer in the 2nd floor zone. No drips.
If I leave the feeder valve on, system cold sits at 10psi, and immediately blows off at 30psi as its coming up to temp. Frankly, I'm kind of stumped. Everything seems to be in working order and functioning individually, just as a whole, something is throwing it off, cant find the happy medium.